In the 1950s, researchers discovered that molten glass conducts electricity. This led to the development of electric furnaces, where heat could be supplied to molten glass by passing an electric current through it via electrodes submerged in the melt.2
Glass melting electrodes are exposed to extremely high temperatures and aggressive chemical conditions. Subsequently, molybdenum was ideal for early electric furnaces, exhibiting the required combination of heat resistance, corrosion resistance and high electrical conductivity (2×107 S/m). Other materials such as platinum, tin oxide, carbon and nickel alloys like Inconel have since found limited use in glass melting electrodes, however these materials suffer from fragility and low strength at the required temperatures.
Molybdenum remains the material of choice for electric-boost, gas-fired furnaces today, occasionally alloyed with a small amount of zirconium to improve corrosion resistance. Advanced coatings can even enable molybdenum-based materials to be brought up to temperature in air without oxidation.